Reciprocating pump



Jan. 28, 96 R. w. MANN ETAL 3,119,280

RECIPROCATING PUMP Filed May 3, 1961 2 Sheets-Sheet 1 mvsurors ROBERT w.MANN BY sown a. LINDSAY JR.

ATTORNEYS Jan. 28, 1964 R. W..MANN ETAL 3,119,280

RECIPROCATING PUMP Filed March 3. 1961 2 Sheets-Sheet 2 INVENTORS ROBERTW. MANN BY EDWARD R. LINDSAY TR.

ATTORNEYS United States Patent 3,119,280 RECIPROCATING PUMP Robert W.Mann, Lexington, and Edward R. Lindsay, In,

This invention relates to an improved diaphragm pump provided with suchfeatures as substantially complete protection of the drive system frompump head leakage and simple, yet accurate adjustment of the pumpstroke. The pump head includes an unstressed barrier diaphragm (11S-posed behind a conventional pumping diaphragm so that fluid leakingthrough the latter member is prevented by the barrier from escapingfurther into the interior of the pump housing. The drive mechanismincludes an axially adjustable eccentric bearing mounted on a skewedcylmder, the position of the bearing on the cylinder determining thelength of the pumping stroke.

A principal object of our invention is to provide a diaphragm pump withimproved protection against leakage of the pumped fluid into the drivemechanism of the pump. This feature of the pump materially reducescorrosion attributable to seepage of pumped fluids onto vulnerablemechanical parts.

Another object of the invention is to provide an improved pump head fora pump of the above character.

A further object of the invention is to provide an improved drivemechanism for a reciprocating pump particularly a diaphragm pump of theabove type.

Yet another object of our invention is to provide a drive mechanism ofthe above type having an accurate stroke adjustment readily operable byunskilled personnel.

Other objects of the invention will in part be obvious and will in partappear hereinafter. The invention accordingly comprises the features ofconstruction, combination of elements, and arrangement of parts whichwill be exemplified in the construction hereinafter set forth, and thescope of the invention will be indicated in the claim.

'For a fuller understanding of the nature and objects of the'i-nvention,reference should be had to the following detailed description taken inconnection with the accompanying drawing, in which:

FIGURE 1 is a horizontal plan view, partly in section, looking down intothe interior of a pump incorporating the features of our invention, and

FIGURE 2 is a side elevation, partly in section, of the portion of thepump containing the pumping diaphragm and associated parts.

Referring to FIGURE 1, a pump embodying the features of our inventionmay be enclosed within an upper housing generally indicated at 16,mounted on a lower housing, generally indicated at 12, integral with abase flange 14. As shown in the drawing, the housing 16 may take aroughly cylindrical form with a horizontally disposed axis, while thehousing 12 may be a vertically dis posed cylinder. A motor 16, disposedwithin the lower housing 12, has a shaft 18 extending upwardly into thehousing to actuate a drive mechanism for the pump.

In a manner to be described, the drive mechanism converts the rotarymotion of the shaft 18 into a reciprocating motion imparted to a pumprod generally indicated at 20. The rod 20 extends into an extension ofthe housing,

generally indicated at 22, where it actuates a pumping diaphragmoperating in conjunction with other parts in the manner of aconventional diaphragm pump.

The drive mechanism includes a worm 24 fastened to the shaft 18 andmeshing with a worm Wheel 26. The worm wheel 2-6 is keyed to a shaftgenerally indicated at 28, rotating in bearings 30 and 32. The bearing39 is 3119,28 Patented Jan. 28, 1964 mounted in a plate 34 held againsta shoulder 36 in the housing 10 by a series of shoulder screws 38working against a cover plate 40. The bearing 32 is mounted in an endplate 42 secured to the housing 10 by bolts 44 and preferably providedwith an. O-ring seal 46. i

A skewed cylinder 48 is preferably formed integrally with the shaft 28for rotation about the axis of the'shaft. A bearing generally indicatedat 50 is mounted on the cylinder 43 by means of a bushing 52.. Theinterior surface of the bushing $2 is preferably canted at the sameangle as the cylinder 48, and, thus, the axis of the bearing 50 isparallel to the axis of rotation of the shaft 28. Thetwo axes do notnecessarily coincide, and, whenlthey do not, rotation of the shaft 28imparts an eccentric motion to the bearing 50. When projected onto thehorizontal plane (the plane of the drawing), this motion isreci'procato-ry in a direction perpendicular to the axis of the shaft28. The reciprocation is imparted to the rod 20, which has an end 54 incontact with the outer race 56 of the hearing 50. i

More specifically, for the purpose of the describing the eccentricmotion of the bearing'Sl), the inner race '58 thereof, together with thebushing 52 and cylinder 4'8, may be considered as one solid member. Ifthe position of the bushing 52 on the cylinder 48 is such that the axisof the bearing 50 coincides With the axis of the s'haftg28, the innerrace 58 will undergo a perfectly circular motion upon rotation of theshaft 28. In other words, the shaft, in effect, passes through thecenter of a disk comprising the inner race, bushing and skewed cylinder.

In theposition illustrated, however, the bearing 50 is located on aportion of the cylinder 48 where the axes of the bearing and the shaftdo not coincide. in effect, the shaft 2-8 passes through an off-centerportion of a disk, and the periphery of the disk (the inner race 50,)undergoes an eccentric rather than circular motion. The amount ofeccentricity, i.e., the amplitude of the oscillatory motion described byinner race 50*, increases with the distance between the axis of shaftrotation and the axis of the bearing 50, and this, in turn, dep ends onthe position of the bushing 52 longitudinally along the cylinder 48. Inthe drawing, the position of the bushing corresponds to maximumeccentricity. If the bushing is moved to the left along the cylinder 48,the two aXes move closer together, and the eccentricity is therebyreduced. Thus, the length of the pump stroke may be varied by moving thebushing 52 and bearing 50 thereon longitudinally along the cylinder 48.

Adjustment of the pumping stroke is effected by rotation of a knob 61}connected to the bearing 50 by way of a screwthread and linkage,whichconverts the rotary motion of the knob into transverse motion along.the axis of the shaft28. The knob 60 is arfixed to a shaft 62 fastenedto a threaded slug 64 by means of a pin 66. ,An oversized portion 62a ofthe shaft 62 bears against a bearing 68, and the slug 64 is in contactwith 'a bearing 70, thereby preventing axial movement of the slug.

The thread on the slug 64 meshes with the thread in a plate 72 securedbetween sleeves. 74 and nuts, 76i0n bolts 78. The bolts 78, in turn, aresuitably fastened to a ring 811* fastened to the bearing 50. Moreparticularly, the ring 8t is sandwiched between a segmented clamp82 andan annular plate 84, the plategbeing secured to the clamp by means ofscrews 86. The clampBZ, which is in two or more segments, has 'aprojecting rim 82a extending into a circumferential groove 56a in theouter race 56. Radial displacement of the segments forming the clamp 82is prevented by their attachment to the plate 84, which maintains themas a unified structure. The plate 34 is also provided with clearanceholes 88 permitting relative motion between the bearing 50 and theclamping structure :afiixed thereto, on the one hand, and the ring 80and bolts 78 on the other hand.

Accordingly, rotation of the knob 69 provides axial displacement of thebearing 50 and bushing 52 by way of the plate 72, bolts 78 and theclamping structure enclosing the ring 80. For accurate calibration ofthe stroke, the circumferential surface 60a of the knob 69 may beprovided with suitable indicia, generally indicated at 90, accessiblethrough a window in a tube 92 preferably integral with the cover plate40. Adjustment of the pump stroke is linear with respect to rotation ofthe knob 60. That is, rotation of the knob through a given angleprovides the same increment in stroke length regardless of the positionof the knob. This makes calibration of the indicia 90 a relativelysimple procedure and also facilitates adjustment of the pump stroke byservo or other automatic means connected to the shaft 62. Linear controlof the stroke will, of course, also be obtained such means are connecteddirectly to the bearing 50.

While the outer race 56 of the bearing 50 does not follow the rotarymotion of the inner race 58 about the axis of the bearing, it doesundergo the eccentric motion of the bearing about the axis of rotationof the shaft 23. In other words, its motion is described by the rotationof the bearing axis about the shaft axis. This results in a slidingengagement of the clamp 82 and plate 84 with the ring 80, which isstationary with respect to rotation of the shaft 28. However, forseveral reasons, the frictional wear between these parts is minimal. inthe first place, the amount of the relative motion between them for eachrevolution of the shaft 28 is quite small. In the second place, theinterior of the housing is preferably partially filled with a suitablelubricant, thereby minimizing friction. Furthermore, the angle betweenthe axis of the cylinder 48 and that of the shaft 28 is kept small, sothat minimal axial forces on the bearing 50 are developed by itsmovement against the pump rod, and the frictional forces between thering 8% and the members engaging it are negligible insofar as theproblem of wear is concerned.

It should also be noted that, with the construction described above,there is a slight rolling contact between the outer race 56 and the endof the rod 20. However, there is essentially no sliding contact betweenthese parts, and, thus, wear on the engaging surfaces thereof is also ata minimum.

The housing extension 22 supports a pump head 94- affixed by means ofscrews (not shown) extending into an annular spacer 114. The spacer 114,in turn, is aflixed to the housing extension .22 by means of furtherscrews (not shown) isolated from the screws holding the head 94. As seenin FIGURE 2, a pair of check valves 98 and 100 are disposed betweeninlet and output lines 102 and 104 and passages 105 and 106communicating with a pumping chamber 110. A pumping diaphragm 1=12,secured to the pump rod 2! reciprocates with the rod to provide apumping action in the chamber 110.

The outer edge of the pumping diaphragm 112 is clamped between the pumphead and the spacer 114, while the outer edge of a barrier diaphragm 116is disposed between the spacer and the extension 22. The inner edge ofthe diaphragm 112 is clamped against a backing memher 118 by the head119a of a screw 119 threaded into the backing member. The member 118, inturn, has an integral stud 1121 extending through a support disk 121)and threaded into the pump rod 20. The inner edge of the diaphragm 116is thus clamped between the member 118 and the disk 120.

The pump rod 20 rides in a sleeve 124 secured in the housing extension22. Leakage of lubricant from the housing 10 is prevented by a shaftseal 124a. A s ring 130, bearing against an inner annular portion 22a ofthe housing extension 22 and a washer 132 and snap ring 132a affixed tothe rod 20, urges the rod 20 against the outer race 56 of the bearing 50and thus causes the rod to follow the projected motion of the outer racein the horizontal plane.

The backing member 118 preferably has a diameter only slightly less thanthe interior diameter of the pump head 22, and, thus, its reciprocationthereof by the rod 20 provides an essentially piston-like action withinthe chamber 1 10, particularly with the pressure compensation describedbelow.

Should the pumping diaphragm rupture, fluid leaking rearwardly thereofwill encounter the barrier diaphragm 115, which prevents it from seepinginto the interior of the housing 10. It will be noted that the diaphragm116 is of a rolling .fold type. Thus, the barrier diaphragm is under notension during operation of the pump, and, thus, combined with its limpnature, minimizes fatigue and extends its life materially beyond that ofthe pumping diaphragm 112. Thus, assuming that both diaphragms arereplaced whenever the pumping diaphragm deteriorates, there is completeinsurance against leakage of the pumped fluid into the drive mechanism.The spacer 114 is provided with a valve generally indicated at 134 whichvents the space between the pumping and barrier diaphragms and thusprevents a build-up of fiuid pressure against the barrier diaphragm 116upon rupture of the diaphragm 11 2. The valve 134 also controls the airpressure in the chamber 135 between the diaphragms 112 and 116 in suchmanner as to increase the output of the pump.

More specifically, the valve 134 includes an elastomeric disk 136 seatedin a counterbore 137 communicating with the chamber 135 by way of apassage 138. The disk 136 is urged in place, to seal the passage 138 bya weak spring 139 acting between a backing plate 140 and a cup 141threaded into the counter-bore 137. A hole 142 vents the interior of thecup 141 to the atmosphere.

During the forward stroke of the pump rod 20 and backing member 118,i.e., toward the pump head M, the diaphragm 112 tends to wrap around thecurved forward Surface of the member 118 in response to the increasedpressure in the chamber 110. On the return stroke, however, there is apartial vacuum in the chamber 110, and, with atmospheric pressure in thechamber 135, this would pull the diaphragm 112 away from the member 118,thereby shortening the effective length of the pumping stroke.

Operation of the valve 134 rests on the fact that the volume of thechamber 135 is less during the forward stroke of the pump than on thereturn stroke. This is due largely to the configuration of the barrierdiaphragm 116, which has a fold 116a extending rearwardly in the housingextension 22. Thus, during the forward stroke there is a tendency forthe pressure in the chamber 135 to rise, and this opens the valve 134 tomaintain the pressure at almost atmospheric value.

Then, the valve closes, and, on the return stroke, the pressure in thechamber 135 drops. This keeps the pressure differential across thediaphragm 112 at a low level, thereby minimizing the pull of thisdiaphragm away from the member 118. Thus, use of our constructionlengthens the effective stroke of the pumps, with a resultant increasein output of as much as one third.

Since the drive mechanism is preferably immersed in a lubricant, it isdesirable to seal the interior of the housing '10. This may beaccomplished by the use of a gasket 143 (FIGURE 1) between the coverplate 40 and the housing, shaft seal 124a, and the length of the sleeve124 along the pump rod 20, as well as the O-ring seal 46 describedabove. A passage 144 (FIGURE 2) in housing extension 22 vents the spacebehind the barrier diaphragm 1116 and prevents a buildup in pressure ofsuch lubricating fluid as might leak between rod 20 and sleeve 124 andseal 1245: from the housing 10.

From the above, it will be apparent that we have provided an improveddiaphragm pump with greater reliability than prior units of this type.In particular, leakage of the pumped fluid into the drive mechanism hasbeen virtually eliminated. Furthermore, the drive mechanism is simple inconstruction and largely free of wear problems. Yet, it may be adjustedwith a high degree of accuracy even during operation of the pump.

It will also be apparent that many changes may be made in the structurerecited above without departing from the principles of our invention.Thus, the cylinder 48 need not have a circular cross section; forexample, it may be polygonal or fluted, with the bushing 52 shaped tofit. Furthermore, it is not necessary that the shape of the bushing besuch as to maintain the axis of the bearing 50 parallel to the axis ofthe shaft 28-. However, this last condition is desirable, since there isthen a slight rolling contact between the outer race 56 and the end ofthe stub 54, but absolutely no sliding engagement between these parts.Therefore, vvear on the engaging surfaces thereof is at a minimum. Tomaximize this advantage, the pump rod 20 should move perpend-iculary tothe bearing 50 and shaft 28 axes.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

\It is also to be understood that the following claim is intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall there/between.

We claim:

In a reciprocating pump of the type comprising a pump head, a pump rodextending into said purnphead and mounted for axial reciprocationtherein and a drive mechanism for reciprocating said pump rod, theimprovement in which said drive mechanism comprises a shaft mounted forrotation about a first axis, a cylinder on said shaft and rotatingtherewith, said cylinder having an axis angled to said first axis, abearing unit mounted on said cylinder and extending around thecircumference thereof, said pump rod being in contact with said bearingunit along a circumferential surface thereof, adjusting means for movingsaid bearing unit axially of said shaft, means for rotating said shaft,said bearing unit including a frictionless bearing having an inner raceconforming to the circumferential surface of said cylinder and an outerrace mounted for relative rotation with respect to said inner race aboutan axis parallel to said first axis, said adjusting means including anannular member disposed around and spaced from said shaft, meansclamping said annular member to said outer race in such manner as topermit relative motion of said annular member and said outer raceradially with respect to said shaft and prevent relative motion axiallywith respect to said shaft, said annular member being radially fixedwith respect to said shaft, and means for moving said annular memberaxially along said shaft.

References Cited in the file of this patent UNITED STATES PATENTS540,843 Richards June 11, 1895 2,083,073 Loeber June 8, 1937 2,323,950Wade July 13, 1943 2,326,474 Malsbary et a1 Aug. 10', 1943 2,356,993Glasner et a1 Aug. 29, 1944 2,414,806 Finney Jan. 28, 1947 2,544,055Staats Mar. 6, 1951 2,612,837 Midgette Oct. 7, 1952 2,776,573 Willi Jan.8, 1957 2,900,839 Mackintosh Aug. 25, 1959

